Should I throw an error or return a rejected promise inside an async function?

I'm working with the promises provided by the AWS JS SDK. The gist of what I'm doing when I create an async function that wraps the AWS SDK looks like this:

module.exports.myCustomFunction = input => {

    if (badInput) {
        throw new Error('failed') // <-- This is they key line
    }

    return sns.createTopic(someParams).promise()
}

// The caller looks like this:
myModule.myCustomFunction(someInput).then(result => {
    // carry on
})
.catch(err => {
    // do something with the error
})

I was approached by someone who said that I should never throw an error inside these kinds of promise-based functions. They suggested returning Promise.reject('failed') instead. To be honest I'm not that well versed in promises yet so their explanation kind of went over my head.